Folded vertical monopole antenna



1967 R. c. FENWICK ETAL 3,

FOLDED VERTICAL MONOPOLE ANTENNA Filed 001,. 11, 1965 I N VEN'IORSRICHARD C. FENWICK ROGER A. MAR'KLEY BY ATTORNEY United States PatentIowa Filed Oct. 11, 1965, Ser. No. 494,348 6 Claims. (Cl. 343--845) Thisinvention relates in general to antennas and in particular to anumbrella-shaped vertical antenna.

It is an object of this invention to provide an antenna which has highefficiency and broad bandwidth.

Another object of this invention is to provide an antenna which consistsof two short vertical monopole elements which are connected togetherwith a half wavelength transmission line. The half wavelength line iswound back and forth about the surface of an imaginary solid which cantake many alternate forms.

An antenna constructed for low frequencies results in a relatively longhalf wavelength and such length can be formed into a relatively smallspace by winding the half wavelength in the form of a cone or pyramid.

A feature of this invention is found in the provision for a pair ofshort monopole elements which are connected together with a halfwavelength transmission line formed to define a surface of a cone orpyramid.

Further objects, features and advantages of this invention will becomeapparent from the following description and claims when read in view ofthe accompanying drawings, in which:

FIGURE 1 is a perspective view of an antenna constructed in accordancewith this invention;

FIGURE 2 illustrates a modification of the invention; and,

FIGURE 3 illustrates a further modification of the invention.

In the low frequency range of 15 to 60 kilocycles, it is desirable toprovide an efficient and compact antenna. Since half wavelengths atthese frequencies are considerable, the present antenna has beendeveloped in which a half wavelength portion is formed into a conical orother surface and has its opposite ends connected to two monopoleelements. Such a structure has been determined to have a high efficiencyand a relatively broad bandwidth.

FIGURE 1 illustrates an antenna constructed according to the teachingsof this invention.

A ground plane is generally designated as and supporting mast 11 has itslower end 12 firmly attached to the ground plane. In a particularembodiment, such an antenna might extend over one thousand feet in theair.

The top end 13 of the mast 11 has attached to it a first section 14 of awound half wavelength conductor 15. The half wavelength conductor iswound to form a cone from the end of the mast to a plane A which is adistance X above the ground plane 10. From the end 17 of the slantportion 14, a radial portion 18 extends to an insulating disc 20 closelyadjacent the mast 11 and is then carried upwardly by a section 19 to aninsulating disc 21 which is attached adjacent the top of the mast 13. Asecond slant portion 22 extends from the disc 21 to plane A and then ina radial portion 23 to the mast 11 and back to disc 21 and so on aboutthe mast. The second end 24 of the 3,345,635 Patented Oct. 3, 1967 ice.

j 2. J conductor 15 is connected to a second vertical monopole 31 whichhas its lower end connected to a coax feed line 32. To support the mast11 and the half wavelength conductor 15 suitable guy'wire's 33 areattached to the junctions between sections 14 and 18 and 22 and 23 byinsulators 34. The lower ends of guy wires 33 are attached to suitableanchors mounted in the ground.

The mast 11 and conductor 31 constitute a pair of monopoles which areconnected by the half wavelength line consisting of the conical shapedwinding illustrated. By forming the winding into a conical shape, thespacial requirements of the antenna are substantially reduced and arelatively compact structure results. Since the guys are insulated fromthe ground plane and the half wavelength conductor 15, they do not forma part of the radiating structure of the antenna.

FIGURE 2 illustrates a structure similar to the configuration of FIGURE1 except that the half wavelength winding 36 is wound differently toeliminate the vertical lengths 19 of FIGURE 1. The winding 36 extendsfrom end 13 of mast 11 to plane A in a section 37. Then to disc 20adjacent the mast and then radially out from the mast in a section 39 toplane A. Then upwardly to disc 21, etc., until the antenna is completelyformed. The end 44 is joined to a coax feed line 46.

Another modification of the invention is illustrated in FIGURE 3 whereinthe feed monopole .50 and grounded monopole 11 are connected by a spiralwinding designated generally as 51 which passes upwardly about animaginary conical surface from the end 52 of feed monopole 50 to theupper end 13 of the grounded monopole 11. Suitable guy wires 53 andinsulators 54 support the structure.

Although the half wavelength windings have been shown in the form of acone, it is to be realized that a pyramid with any number of sides couldalso be used. The cone or pyramid apex angle at the top of the mastshould be kept as close to degrees as possible but for very largestructures, angles in the range of 45 to 55 degrees would normally beused.

Although this invention has been described with respect to particularembodiments thereof, it is not to be so limited, as changes andmodifications may be made therein which are within the spirit and scopeof the invention as defined by the appended claims.

We claim:

1. An antenna comprising a pair of monopole radiating elements extendingin the same general direction, one of said monopoles being connected toground and the other of said monopoles being connected to a signalsource, a single continuous half wavelength transmission line sectionconnecting the ends of the monopole radiating elements, and the halfwavelength section of line wound about the surface of an imaginary coneso as to dimensionally shorten the half wavelength section and producean antenna which requires a small space.

2. An antenna comprising a pair of monopoles, one of the monopolesconnected to the ground plane and being rigid to provide mechanicalsupport, the other of said monopoles being connected to a signal source,a single continuous half wavelength transmission line section with oneend attached to the upper end of the rigid monopole and folded about thesurface of an imaginary cone, and

the other end of the half wavelength line connected to the secondmonopole.

3. In apparatus according to claim 2 wherein said sur face defined bythe half wavelength line consists of a pyramid.

4. In apparatus according to claim 2 guy Wires insulatingly attached tothe half wavelength line at certain points and to the ground to supportthe line in a surface and to guy the mast.

5. In apparatus according to claim 2 wherein the cone is formed byslanting portions which extend downwardly and outwardly from the top ofthe mast.

6. In apparatus according to claim 1 wherein said cone is formed byspirally winding the line from the top of the grounded. monopole.

References Cited UNITED STATES PATENTS 7/1953 Smeby 343-802 12/1960Radford 343--899 8/1961 Josephson 343--829 8/1961 Seeley 343-875 2/1964Heisrath 343866 5/1966 Tanner 343891 FOREIGN PATENTS 6/ 1935 GreatBritain.

ELI LIEBERMAN, Primary Examiner.

15 R. F. HUNT, Assistant Examiner.

1. AN APPARATUS COMPRISING A PAIR OF MONOPOLE RADIATING ELEMENTSEXTENDING IN THE SAME GENERAL DIRECTION, ONE OF SAID MONOPOLES BEINGCONNECTED TO GROUND AND THE OTHER OF SAID MONOPOLES BEING CONNECTED TO ASIGNAL SOURCE, A SINGLE CONTINUOUS HALF WAVELENGTH TRANSMISSION LINESECTION CONNECTING THE ENDS OF THE MONOPOLE RADIATING ELEMENTS, AND THEHALF WAVELENGTH SECTION OF LINE WOUND ABOUT THE SURFACE OF AN IMAGINARYCONE SO AS TO DIMENSIONALLY SHORTEN THE HALF WAVELENGTH SECTION ANDPRODUCE AN ANTENNA WHICH REQUIRES A SMALL SPACE.